1. Field of the Invention
This invention relates to shot cleaning apparatus and more particularly it concerns improvements involving novel auxiliary impellers and gravity feed systems for such apparatus.
2. Description of the Prior Art
U.S. Pat. No. 3,540,155 shows a shot cleaning apparatus in which a paddle blade impeller is mounted inside a housing to throw shot upwardly in the housing. A workpiece holder, in the form of an open mesh cage, is mounted inside the housing above the impeller in the path of the upwardly thrown shot. After the shot strikes the workpieces inside the cage it falls back down inside the housing and is collected in a hopper. The hopper is located above the center of rotation of the impeller and is constructed and arranged to direct the collected shot, by gravity, back into the rotating impeller which throws the shot back up at the workpiece.
The above described shot cleaning apparatus has the advantage that no moving parts other than the rotating impeller itself are needed for recirculation of the shot. All recirculation is carried out by the action of the impeller blades and by gravity.
Other shot cleaning devices use impellers arranged at various levels and locations around the workpiece so that shot will be thrown at the workpiece from different directions. This ensures that all surfaces of the workpiece will be cleaned by the shot. Such other shot cleaning devices however require special powered shot recirculation systems such as screw conveyors and bucket elevators to transfer the shot back to the various impellers.